Preparation of a Family of Hexanuclear Rhenium Cluster Complexes Containing 5-(Phenyl)tetrazol-2-yl Ligands and Alkylation of 5-Substituted Tetrazolate Ligands

The preparation of two new families of hexanuclear rhenium
cluster
complexes containing benzonitrile and phenyl-substituted tetrazolate
ligands is described. Specifically, we report the preparation of a
series of cluster complexes with the formula [Re6Se8(PEt3)5L]2+ where L = benzonitrile, p-aminobenzonitrile, p-methoxybenzonitrile, p-acetylbenzonitrile, or p-nitrobenzonitrile.
All of these complexes undergo a [2 + 3] cycloaddition with N3– to generate the corresponding [Re6Se8(PEt3)5(5-(p-X-phenyl)­tetrazol-2-yl)]+ (or [Re6Se8(PEt3)5(2,5-p-X-phenyltetrazolate)]+) cluster
complexes, where X = NH2, OMe, H, COCH3, or
NO2. Crystal structure data are reported for three compounds:
[Re6Se8(PEt3)5(p-acetylbenzonitrile)]­(BF4)2•MeCN,
[Re6Se8(PEt3)5(2,5-phenyltetrazolate)]­(BF4)•CH2Cl2, and [Re6Se8(PEt3)5(2,5-p-aminophenyltetrazolate)]­(BF4). Treatment of [Re6Se8(PEt3)5(2,5-phenyltetrazolate)]­(BF4) with HBF4 in CD3CN at 100 °C leads to
protonation of the tetrazolate ring and formation of [Re6Se8(PEt3)5(CD3CN)]2+. Surprisingly, alkylation of the phenyl and methyl
tetrazolate complexes ([Re6Se8(PEt3)5(2,5-N4CPh)]­(BF4) and [Re6Se8(PEt3)5(1,5-N4CMe)]­(BF4)) with methyl iodide
and benzyl bromide, leads to the formation of mixtures of 1,5- and
2,5-disubstituted tetrazoles.